As noted, processes and compositions for the reduction of nitrogen oxides in effluents from the combustion of carbonaceous fuels have been developed extensively over recent years. With the increased attention to the health risks and environmental damage caused by agents such as smog and acid rain, it is expected that NO.sub.x reduction research will continue to be pursued.
Selective catalytic reduction processes for reducing nitrogen oxides levels are well known and utilize a variety of catalytic agents. For instance, in European Patent Application WO 210392, Eichholtz and Weiler discuss the catalytic removal of nitrogen oxides using activated charcoal or activated coke, with the addition of ammonia, as a catalyst. Kato et al. in U.S. Pat. No. 4,138,469 and Henke in U.S. Pat. No. 4,393,031 disclose the catalytic reduction of NO.sub.x using platinum group metals and/or other metals such as titanium, copper, molybdenum, vanadium, tungsten, or oxides thereof with the addition of ammonia to achieve the desired catalytic reduction.
Another catalytic reduction process is disclosed by Canadian Patent 1,100,292 to Knight which relates to the use of a platinum group metal, gold, and/or silver catalyst deposited on a refractory oxide; and Mori et al. in U.S. Pat. No. 4,107,272 discuss the catalytic reduction of nitrogen oxides using oxysulfur, sulfate, or sulfite compounds of vanadium, chromium, manganese, iron, copper, and nickel with the addition of ammonia gas.
In a multi-phase catalytic system, Ginger, in U.S. Pat. No. 4,268,488, discloses exposing a NO.sub.x containing effluent to a first catalyst comprising a copper compound such as copper sulfate and a second catalyst comprising metal combinations such as sulfates of vanadium and iron or tungsten and iron on a carrier in the presence of ammonia.
In addition, in a process which combines SNCR and SCR technology to reduce nitrogen oxides while greatly minimizing the cost of the SCR aspect of the process, Hofmann, Sun, and Luftglass, in U.S. Pat. No. 4,978,514, disclose a process involving first reducing NO.sub.x via an SNCR process using a nitrogenous treatment agent and then contacting the treated effluent with a nitrogen oxides reducing catalyst.
What is desired, therefore, is a process which permits the reduction of effluent nitrogen oxides and plume opacity in gas turbines without the art-recognized drawbacks of the injection of water directly into the combustion can while reducing the capital outlay attendant to the use of an SCR process alone.